This application claims benefit of Japanese Patent Application(s) No. 2000-17312 filed in Japan on Jan. 26, 2000, the contents of which are incorporated by this reference.
The present invention relates generally to an optical element with variable optical properties and an optical device using the same, and more particularly to a variable hologram element and an optical device using the same.
Among optical elements so far known to have variable optical properties, there is such a liquid crystal lens arrangement 901 as shown in FIG. 23. A light beam incident from the left of the paper is merely converted through a polarizing plate 902 to polarized light, which is then incident on a liquid crystal lens 903. When the voltage applied on the liquid crystal 904 of the liquid crystal lens 903 is held off, liquid crystal molecules 905 are oriented as shown and the refractive index of the liquid crystal 904 is so increased that the liquid crystal lens can act as a convex lens. When the voltage is put on, the liquid crystal molecules 905 are oriented parallel to an optical axis 906, resulting in a decrease in the refractive index of the liquid crystal 904. This causes the convex lens action of the liquid crystal lens to become slender. However, a problem with this liquid crystal lens arrangement 901 is that the amount of light available is limited to about 40% due to the presence of the polarizing plate 902. In FIG. 23 reference numerals 907, 908 and 909 represent a transparent electrode, a switch and an AC source, respectively.
In view of such a problem with the prior art as mentioned above, an object of the present invention is to provide an optical element with variable optical characteristics, which ensures an increased amount of light, and an optical system using the same.
The variable hologram element according to the present invention, for instance, is characterized by making use of a polymer dispersed liquid crystal or a polymer stabilized liquid crystal.
In this case, the substrate may have a lens or mirror action.
It is then preferable to meet at least one of conditions (1), (4), (8), (10) and (11).
A plurality of variable hologram elements may be laminated together with a transparent electrode interposed between them.
Using this variable hologram element, a finder for an image pickup device may be constructed.
Preferably in this case, the finder includes a light source having a short half bandwidth.
It is also preferable to meet at least one of conditions (5) and (6).
A finder for a digital camera may be constructed using the aforesaid variable hologram element.
A single-lens reflex, Galilean or Albada type finder may be constructed, using the aforesaid variable hologram element.
A wearable information device may also be constructed, using the aforesaid variable hologram element.
Preferably in this case, the wearable information device is used with a light source having a short half bandwidth.
The variable hologram element may be used for an adapter or case.
The wearable information device may also be used in the form of a head mount display.
In this case, the head mount display may be designed to have functions of glasses and a display.
A display for an image pickup device may be constructed, using the aforesaid variable hologram element.
Preferably in this case, the display includes a light source having a short half bandwidth.
The variable hologram element may be used for an adapter or case.
Variable-focus glasses may be constructed, using the aforesaid variable hologram element.
Preferably in this case, the glasses include a light source having a short half bandwidth.
Alternatively, the glasses are preferably used with a light source having a short half bandwidth.
An optical pickup may be constructed, using the aforesaid variable hologram element.
An optical pickup for disks with varying thicknesses may also be constructed, using the aforesaid variable hologram element.
Preferably in such cases, the optical pickup is preferably used with a light source having a short half bandwidth.
An optical measuring device may be constructed, using the aforesaid variable hologram element for optical path switching.
An optical measuring device may be constructed, using the aforesaid variable hologram element.
Preferably in such cases, the optical measuring device is preferably used with a light source having a short half bandwidth.
A decentration measuring device may be constructed, using the aforesaid variable hologram element for optical path switching.
A decentration measuring device may be constructed, using the aforesaid variable hologram element.
Another variable hologram element of the present invention is characterized by comprising a liquid crystal impregnated into interstitial voids in a photonic crystal.
Yet another variable hologram element of the present invention is characterized by comprising a photonic crystal and a liquid crystal.
The present invention also encompasses an endoscope characterized in that an image is formed by a digital hologram.
Preferably in this case, the endoscope satisfies condition (12).
The endoscope may also be designed in such a way as to form an image by a digital hologram using infrared light.
Preferably in this case, visible light is observable.
The endoscope may include a trichromatic light source.
When an image is formed by a digital hologram using infrared light, it is preferable to meet condition (13).
The endoscope may also include a half-silvered mirror prism.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.